Position detection device and position indicator thereof

Abstract

The present invention relates to a position detection device and a position indicator thereof. Consumption of a battery of an active stylus is suppressed, and transmission time of a signal from the active stylus is suppressed. The position detection device of the present invention is a position detection device (1) in which a tablet (3) and a power supply device built-in stylus (2) bidirectionally perform signal transmission and reception by an electrostatic coupling method, and is configured to transmit an instruction signal US_cmd after transmitting a trigger signal US_trg for starting an instruction information reception section for receiving an instruction signal US_cmd containing information for controlling the stylus (2) to the stylus (2).

Description

[0001] This application is a divisional application of the application filed on August 3, 2015, with application number 201580081089.1, entitled "Position Detection Device and Position Indicator Thereof". Technical Field

[0002] The present invention relates to a position detection device and a position indicator, and more particularly to a position detection device and the position indicator for determining the indicated position of a position indicator on a tablet computer by means of electrostatic coupling between a tablet computer and a position indicator built into a power supply device. Background Technology

[0003] Position detection devices are known to transmit signals from a power supply-built position indicator, i.e., an active stylus (hereinafter referred to as "stylus"), to a tablet computer via electrostatic coupling. In such position detection devices, communication is typically one-way: the stylus transmits the signal, which is then received by the tablet computer. Patent Document 1 discloses an example of such a position detection device.

[0004] Patent Document 2 discloses another example of a position detection device. In this example, the stylus includes electrodes for signal transmission and a battery, and transmits the results of pen pressure detection digitally. Furthermore, the tablet computer comprises a display device and a transparent sensor, forming a structure capable of detecting both the stylus's indicated position and the pen pressure, as well as the finger's touch position, through the transparent sensor.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Application No. PCT / JP2014 / 051296

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-63249

[0009] Patent Document 3: Japanese Patent Application Publication No. 2015-103143 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] As disclosed in Patent Document 1, the stylus stores inherent identification information (inherent ID). Conventional styluses are configured to transmit the inherent ID when sending signals toward a tablet computer. However, as disclosed in Patent Document 1, the inherent ID is sometimes a long data set of 60 bits or more, so transmitting the inherent ID would increase the signal transmission time.

[0012] Furthermore, as mentioned above, conventional position detection devices that include a stylus communicate from the stylus to the tablet computer, thus requiring continuous signal transmission even when the stylus is not on the tablet. Consequently, conventional styluses suffer from rapid battery drain.

[0013] Furthermore, even when the stylus is on a tablet, the aforementioned inherent ID is information that does not need to be sent multiple times from the position indicator once recognized on the tablet side. However, in conventional styluses as disclosed in Patent Document 1, the inherent ID needs to be sent repeatedly, thus increasing the transmission time from the position indicator and causing more severe battery drain.

[0014] Therefore, one of the objectives of the present invention is to provide a position detection device and a position indicator that can suppress battery consumption of a stylus (a type of position indicator with a built-in power supply) compared to the past, and can also suppress the transmission time of signals sent from the stylus.

[0015] Methods for solving problems

[0016] The position detection device of the present invention is a position detection device that determines the indicated position of the position indicator on the tablet computer by electrostatic coupling between the tablet computer and the position indicator, and has the following basic structure.

[0017] That is, the feature is that the tablet computer sends a first control signal and a second control signal to the position indicator as two control signals with different frequencies or modulation forms for controlling the position indicator. The position indicator has a power supply unit, sends at least a position indication signal to the tablet computer, and is respectively provided with a first control signal receiving unit for receiving the first control signal and a second control signal receiving unit for receiving the second control signal. (Basic Structure 1)

[0018] The position detection device of the present invention is based on the aforementioned basic structure 1, characterized in that the first control signal is a signal of a predetermined single frequency and without modulation, and the second control signal is a signal modulated by predetermined binary data. (Basic Structure 2)

[0019] The position detection device of the present invention is based on the aforementioned basic structure 2, characterized in that the position indicator includes a first operation mode in which only the first control signal is received, and a second operation mode in which the position indicator signal is transmitted and the second control signal is received at least repeatedly. In the first operation mode, the device transitions to the second operation mode upon receiving the first control signal. (Basic Structure 3)

[0020] The position detection device of the present invention is based on the aforementioned basic structure 3, characterized in that the position indicator has inherent ID information or a pen pressure detection circuit, and transmits a data signal modulated according to the detected pen pressure information or the inherent ID information. However, at this time, according to the content of the received second control signal, the inherent ID information, pen pressure information, or other information are selected, and a data signal modulated according to the selected information is transmitted. (Basic structure 4)

[0021] Another aspect of the present invention is a position indicator that determines the indicated position on a tablet computer by electrostatic coupling with the tablet computer. In this position indicator, a transmission signal is generated by utilizing the resonance phenomenon of a resonant circuit based on a primary coil and a capacitor of a transformer. A control signal receiving circuit is connected to the secondary side of the transformer, which receives a control signal transmitted from the tablet computer at a frequency near the resonant frequency of the resonant circuit.

[0022] Invention Effects

[0023] According to the present invention, a first control signal of a specified single frequency and a second control signal modulated by specified binary data are sent from a tablet computer to a position indicator. When the position indicator is not on the tablet computer, the transmission of the position indicator signal, which requires more power, and the reception of the second control signal are not performed. Only the reception of the first control signal, which consumes less power, is performed. Therefore, the battery consumption of the position indicator can be suppressed.

[0024] Furthermore, according to the present invention, the information transmitted as a data signal can be changed according to the content of the second control signal received from the position indicator, so it is not necessary to transmit the pen pressure and the inherent ID together each time as in the past, thus suppressing the transmission time from the position indicator and further suppressing battery consumption. Attached Figure Description

[0025] Figure 1 This is a diagram showing the structure of the position detection device 1 according to the first embodiment of the present invention.

[0026] Figure 2 It means Figure 1 A diagram showing the internal structure of the tablet computer 3.

[0027] Figure 3 It means Figure 1 The diagram shows the internal structure of the stylus 2.

[0028] Figure 4 This is a flowchart illustrating the processing flow of the tablet computer 3 according to the first embodiment of the present invention.

[0029] Figure 5This is a flowchart illustrating the processing flow of the stylus 2 according to the first embodiment of the present invention.

[0030] Figure 6 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in the first embodiment of the present invention.

[0031] Figure 7 This is a flowchart illustrating the processing flow of the tablet computer 3 according to the second embodiment of the present invention.

[0032] Figure 8 This is a flowchart illustrating the processing flow of the stylus 2 according to the second embodiment of the present invention.

[0033] Figure 9 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in the second embodiment of the present invention.

[0034] Figure 10 This is a diagram showing the internal structure of the stylus 2 according to the third embodiment of the present invention.

[0035] Figure 11 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in the third embodiment of the present invention.

[0036] Figure 12 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in a modified example of the first embodiment of the present invention.

[0037] Figure 13 This is a diagram showing an example of a command signal used as a spread spectrum symbol.

[0038] Figure 14 This is a diagram illustrating an example of the structure of a matched filter circuit.

[0039] Figure 15 It means Figure 14 The graph shows the relationship between each step and the output.

[0040] Figure 16 This is a diagram illustrating an example of the internal structure of the stylus 2.

[0041] Figure 17 This is a diagram showing the internal structure of the stylus 2, which is a modified example of the third embodiment.

[0042] Figure 18 This is a diagram showing the internal structure of the stylus 2, which is a modified example of the third embodiment. Detailed Implementation

[0043] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0044] Figure 1 This is a diagram showing the structure of a position detection device 1 according to a first embodiment of the present invention. As shown in the diagram, the position detection device 1 is configured with a stylus 2 serving as a position indicator and a tablet computer 3. Figure 2 This is a diagram showing the internal structure of tablet PC 3. Figure 3 This is a diagram showing the internal structure of the stylus 2.

[0045] The stylus 2 is a pen-shaped device, such as... Figure 1 As shown, it is composed of a pen refill 20, an electrode 21, a pen pressure detection sensor 23 (pen pressure detection circuit), a circuit board 24, and a battery 25 (power supply unit).

[0046] The pen tip 20 is a rod-shaped component, arranged such that the axis of the stylus 2 is aligned with the length direction of the pen tip 20. An electrode 21 is formed by coating the surface of the front end 20a of the pen tip 20 with a conductive material. This electrode 21 can be constructed by embedding a conductive material inside the pen tip 20. A pen pressure detection sensor 23 is physically connected to the pen tip 20 and detects the pen pressure applied to the front end 20a of the pen tip 20. As this pen pressure detection sensor 23, a variable capacitance capacitor that varies according to pen pressure, as described in Patent Document 2, can be used, for example.

[0047] Electrode 21 is electrically connected to circuit board 24 to transmit control signals US sent by tablet computer 3. Figure 1 The system detects the trigger signal US_trg and the command signal US_cmd shown, and sends the stylus signal DS to the tablet computer 3. Figure 1 The position signal DS_pos and data signal DS_res are shown. It should be noted that the electrode used to receive the control signal US can be set separately from the electrode used to send the stylus signal DS.

[0048] The tablet computer 3 is composed of a tablet computer-shaped sensor 30 and a sensor controller 31, and the sensor surface 3a of the tablet computer 3 is configured as the upper surface of the sensor 30.

[0049] Figure 2 This is a diagram showing the internal structure of tablet PC 3. Figure 2In this embodiment, the sensor 30 has a structure in which a plurality of linear electrodes 30X, each extending along the Y direction and arranged at equal intervals along the X direction (orthogonal to the Y direction), and a plurality of linear electrodes 30Y, each extending along the X direction and arranged at equal intervals along the Y direction, are arranged in a matrix. Although not shown, the sensor 30 has a transparent plate-shaped glass substrate, and each linear electrode 30X, 30Y is disposed on the back side (inner surface) of the substrate. The surface of the substrate (outer surface) constitutes the sensor surface 3a of the tablet computer 3. When the tablet computer 3 has a display function on the sensor surface 3a, the substrate is disposed on the display surface of a display device (not shown) such as a liquid crystal display, and each linear electrode 30X, 30Y is disposed between the liquid crystal display and the substrate. In this case, each linear electrode 30X, 30Y is preferably made of a transparent conductive material such as ITO (Indium Tin Oxide).

[0050] like Figure 2 As shown, the tablet computer 3 can detect not only the stylus 2 but also human fingers 4. Because the detection methods for the stylus 2 and fingers 4 differ, the tablet computer 3 performs these detections in a time-sharing manner, as detailed later.

[0051] like Figure 2 As shown, the sensor controller 31 is composed of a selection circuit 41, a selection circuit 42, a control circuit 43, a switch 44, 45, an amplifier circuit 46, a gain control circuit 47, a bandpass filter 48, a detection circuit 49, an analog-to-digital converter (AD converter) 50, and an MCU 51.

[0052] Selection circuit 41 is a circuit that selects one or more adjacent linear electrodes 30X based on control signal d from control circuit 43. Similarly, selection circuit 42 is a circuit that selects one or more adjacent linear electrodes 30Y based on control signal c from control circuit 43.

[0053] The X-side electrode and Y-side electrode selected by selection circuit 41 and selection circuit 42 respectively connect either the X-side or the Y-side to the amplifier circuit 46 via switch 45.

[0054] The signal from the stylus 2, amplified by the amplifier circuit 46, is controlled to a certain level by the gain control circuit 47. The signal is then passed through the bandpass filter 48 so that only the frequency components of the signal sent by the stylus 2 can pass through. After being detected by the detector circuit 49, the signal is output as the received signal level from the stylus 2 by the analog-to-digital converter (AD converter) 50.

[0055] Switch 44 is a circuit used to switch whether the Y-side electrode selected by selection circuit 42 is used for receiving or transmitting. When the control signal b from control circuit 43 is low ("0"), the Y-side electrode selected by selection circuit 42 is connected to amplifier circuit 46 via switch 45. Furthermore, when the control signal b from control circuit 43 is high ("1"), the transmit signal a output from control circuit 43 is supplied to the Y-side electrode selected by selection circuit 42 and transmitted from sensor 30.

[0056] The tablet computer 3 has five modes as shown below. The control circuit 43 switches these modes in the following order and controls the various circuits within the sensor controller 31. Each mode will be described in detail below.

[0057] The first mode is for detecting the position of finger 4. In this mode, control circuit 43 sets control signal b to a high level "1" and control signal e to a low level "0". That is, the transmission signal a output from control circuit 43 is supplied to the Y-side electrode selected by selection circuit 42, and a touch detection signal is sent from sensor 30. Moreover, the X-side electrode selected by selection circuit 41 is connected to amplifier circuit 46. At this time, control circuit 43 controls the signal g to make the center frequency of bandpass filter 48 match the frequency of touch detection signal. With this configuration, MCU 51 reads the change in detection signal caused by finger 4 contacting sensor surface 3a and calculates the coordinate position of finger 4.

[0058] The second is to send a trigger signal US_trg (the first control signal) to stylus 2. (See reference...) Figure 1 In this mode, the control circuit 43 sets the control signal b to a high level "1", thereby supplying the transmission signal a output from the control circuit 43 to the Y-side electrode selected by the selection circuit 42, and sending a trigger signal US_trg from the sensor 30. The transmission signal a in this mode is the same as the trigger signal US_trg generated by the trigger signal transmission unit 43a (first control signal transmission unit), which is part of the control circuit 43. In this embodiment, it is preferably the same frequency as the signal sent by the stylus 2 as described later. Furthermore, the trigger signal US_trg is preferably an unmodulated signal with a single frequency.

[0059] At this time, the selection circuit 42 may select the electrode near the stylus 2 in electrode 30Y and send the trigger signal US_trg, or the Y selection circuit 42 may select all electrodes of electrode 30Y at the same time and send the trigger signal US_trg.

[0060] The third is to send the command signal US_cmd (the second control signal) to stylus 2. (See reference...) Figure 1In this mode, the control circuit 43 also sets the control signal b to a high level "1", thereby supplying the transmission signal a from the control circuit 43 to the Y-side electrode selected by the selection circuit 42. The transmission signal a in this case is the same as the instruction signal US_cmd generated by the instruction signal transmission unit 43b (second control signal transmission unit), which is part of the control circuit 43. It is a signal modulated by the control information (instruction information Cmd described later) used to control the stylus 2. In this embodiment, a spread spectrum symbol is used as the instruction signal US_cmd.

[0061] Figure 13 This diagram illustrates an example of a transmitted signal 'a' as a spread spectrum symbol, showing an example of transmitting a 3-bit instruction (1, 0, 1) with the spread spectrum code "0x1AD3". That is, when the transmitted data is "1", the output signal changes sequentially according to "0x1AD3"; when the transmitted data is "0", the output signal changes sequentially according to the symbol "0xE54C" that inverts "0x1AD3". It should be noted that... Figure 13 The diagram shows the sequence of transmissions starting from the higher-order bits of the spread code.

[0062] At this time, the selection circuit 42 can select the electrode near the stylus 2 in the electrode 30Y and send the command signal US_cmd, or the selection circuit 42 can select all the electrodes of the electrode 30Y at the same time and send the command signal US_cmd.

[0063] The fourth mode detects the position of the stylus 2 by detecting the position signal DS_pos sent by the stylus 2. In this mode, the control circuit 43 sets the control signal b to a low level "0", thereby connecting the Y-side electrode selected by the selection circuit 42 to the amplifier circuit 46 via the switch 45. Furthermore, the control circuit 43 controls the bandpass filter 48 to match the center frequency of the signal sent by the stylus 2 using the control signal g.

[0064] In this embodiment, when determining the X-axis coordinate of the stylus 2, the control circuit 43 sets the control signal e to a low level "0" and connects the X-side electrode selected by the selection circuit 41 to the amplifier circuit 46. For the X-side electrode selected by the selection circuit 41 in this state, multiple X-electrodes, for example, five, centered on the X-electrode closest to the indicated position of the stylus 2, are selected sequentially one by one, and the MCU 51 reads the data output from the AD converter 50 as the signal level value. The MCU 51 determines the X-coordinate of the stylus 2 from the signal level distribution relative to the selected X-electrodes.

[0065] In this embodiment, when determining the Y-axis coordinate of the stylus 2, the control circuit 43 sets the control signal e to a high level "1" and connects the Y-side electrode selected by the selection circuit 42 to the amplifier circuit 46. For the Y-side electrode selected by the selection circuit 42 in this state, multiple Y electrodes, for example five, centered on the Y electrode closest to the indicated position of the stylus 2 are selected sequentially, and the MCU 51 reads the data output from the AD converter 50 as the signal level value. The MCU 51 determines the Y-coordinate of the stylus 2 from the signal level distribution relative to the selected Y electrodes.

[0066] The fifth is receiving the data signal DS_res sent by stylus 2 (see reference). Figure 1 The mode is as follows: When receiving the data signal DS_res, either the X-side electrode or the Y-side electrode can be used, but the case of using the X-side electrode to receive the data signal DS_res is shown here. The control circuit 43 sets the control signal e to a low level "0", thereby connecting the X-side electrode selected by the selection circuit 41 to the amplifier circuit 46. Moreover, the control circuit 43 is controlled by the control signal g to make the center frequency of the bandpass filter 48 match the frequency of the signal sent by the stylus 2. Furthermore, the control circuit 43 is activated so that the selection circuit 41 simultaneously selects multiple X electrodes, for example, three X electrodes centered on the X electrode closest to the indicated position of the stylus 2. In this state, the MCU 51 periodically reads the output from the AD converter 50.

[0067] When using the Y-side electrode to receive the data signal DS_res, simply set the control signal b to low level "0" and the control signal e to high level "1".

[0068] The above describes the operation of control circuit 43 in each mode. As explained above, tablet computer 3 uses the same sensor 30 for both sending and receiving signals. The following will continue the explanation. Figure 2 Other structures within the tablet computer 3 shown.

[0069] Amplifier circuit 46 amplifies the signal guided to the electrode selected from electrodes 30X and 30Y by selection circuit 41 or selection circuit 42. Gain control circuit 47 further amplifies the signal supplied from amplifier circuit 46, and its amplification level can be controlled by control signal f from control circuit 43. The output of gain control circuit 47 is supplied to bandpass filter 48.

[0070] The bandpass filter 48 is a filter circuit that allows only signals of a certain bandwidth centered at a predetermined center frequency to pass through. This center frequency is controlled by a control signal g supplied from the control circuit 43. In the aforementioned finger 4 position detection mode, the control circuit 43 controls the bandpass filter 48 such that the center frequency is equal to the frequency of the touch detection signal. Furthermore, in the aforementioned stylus 2 position detection mode, the control circuit 43 controls the bandpass filter 48 such that the center frequency is equal to the frequency of the position signal DS_pos (see reference DS_pos). Figure 1 The bandpass filter 48 is controlled in a manner equal to the frequency of the received data signal DS_res (see above). Furthermore, the control circuit 43 controls the received data signal DS_res (see above) in a manner equal to the frequency of the received data signal DS_res (see above). Figure 1 In this mode, the bandpass filter 48 is controlled so that the center frequency is equal to the frequency of the data signal DS_res. It should be noted that in this embodiment ( Figure 3 In this configuration, the position signal DS_pos and the data signal DS_res are set to the same frequency.

[0071] Here, the frequency band of the signal used for detection is preferably different from the frequency band of the signals used for stylus detection (position signal DS_pos and data signal DS_res). Therefore, these signals can be sorted by the bandpass filter 48. Furthermore, the data signal DS_res can be a single-frequency signal or a signal containing multiple frequency components; however, in the latter case, the control circuit 43 preferably also controls the bandwidth of the bandpass filter 48 to include all of these multiple frequency components.

[0072] The detector circuit 49 is a circuit that generates a voltage corresponding to the level of the output signal from the bandpass filter 48. The AD converter 50 is a circuit that generates a digital signal by performing analog-to-digital conversion on the voltage corresponding to the received level output from the detector circuit 49 at predetermined time intervals. The sampling time interval of the AD converter 50 is controlled according to a control signal h supplied from the control circuit 43. The digital data output by the AD converter 50 is read by the MCU 51.

[0073] The MCU51, a microprocessor that internally sets up ROM and RAM and operates based on a prescribed program, controls the control circuit 43 by outputting signals a~h from the control circuit 43 as described above, and reads and processes the digital data output by the AD converter 50.

[0074] The control circuit 43 is a logic circuit that is used to accurately output each signal a~h at a specified timing based on the instruction from the MCU 51.

[0075] The above explains the structure and operation of the tablet computer 3. Next, the structure and operation of the stylus 2 will be explained in detail. Figure 16This is a diagram illustrating an example of the internal structure of the stylus 2. Furthermore, Figure 3 This is a diagram showing the internal structure of the stylus 2.

[0076] In the circuit board 24, such as Figure 3 As shown, the internal structure includes three switches SW1~SW3, a control unit 60, an oscillation circuit 61, a transformer 62, a trigger signal detection unit 63, and an instruction information receiving unit 64.

[0077] The oscillation circuit 61 is a circuit that oscillates according to the oscillation control signal Ocn supplied from the control unit 60. The oscillation circuit 61 includes an LC resonant circuit 61a formed by connecting a coil and a capacitor.

[0078] The transformer 62 includes a primary winding (first winding) and a secondary winding (second winding) coupled to each other. The primary winding is used as the winding that constitutes the LC resonant circuit 61a. The secondary winding is connected to the electrode 21 via a switch SW1.

[0079] The trigger signal detection unit 63 is a functional unit (first control signal receiving unit) for receiving the trigger signal US_trg sent by the tablet computer 3, and includes an amplifier circuit 63a and a detector circuit 63b. The amplifier circuit 63a amplifies the trigger signal US_trg guided to the electrode 21, and the detector circuit 63b detects whether the level of the output signal of the amplifier circuit 63a is above a certain level and outputs it as a detection signal Det. The electrode 21 is connected to the amplifier circuit 63a via switches SW1 and SW2.

[0080] The level of the output detection signal Det is "high" when the trigger signal US_trg arrives at electrode 21, and "low" when it does not arrive. In this way, the trigger signal detection unit 63 can output a binary detection signal Det based on the presence or absence of the trigger signal US_trg, even without performing a special decryption operation.

[0081] When the trigger signal detection unit 63 receives the trigger signal US_trg, a transformer 62 is connected to the input side of the amplifier circuit 63a. The primary side of the transformer 62 forms an LC resonant circuit 61a. Therefore, if the frequency of the trigger signal US_trg is made to match the resonant frequency of the LC resonant circuit 61a, the trigger signal detection unit 63 operates in a manner that only detects the trigger signal US_trg in the signal guided to the electrode 21.

[0082] The instruction information receiving unit 64 is a functional unit (second control signal receiving unit) for receiving the instruction signal US_cmd sent by the tablet computer 3, including an AD converter 64a and a matched filter circuit 64b. Figure 14 This is a diagram showing an example of the structure of the matched filter circuit 64b. Figure 14 The matched filter circuit shown includes: a shift register (R0~R31) consisting of 32 segments for storing 12 bits of data; a 16-bit register (k0~K15) for storing a predetermined KEY code; and an arithmetic unit for performing operations on the value stored in the shift register and the KEY code. The arithmetic unit includes a 16-bit register (Q0~Q15) for storing the operation result.

[0083] The instruction information receiving unit 64 is connected to the electrode 21 via switch SW3. When the instruction information receiving unit 64 receives the instruction signal US_cmd, switch SW3 is turned on and switch SW1 is turned off. Details regarding the operation of the instruction information receiving unit 64 will be described later; however, this circuit requires a high-speed clock for operation, resulting in high power consumption. Therefore, in this embodiment, the operation of the instruction information receiving unit 64 can be stopped by the control signal En generated by the control unit 60. Specifically, the instruction information receiving unit 64 is configured to be in an operating state when the control signal En is activated (high level) and in an operating stopped state when the control signal En is not activated (low level). In the operating stopped state, power consumption can be suppressed, and even if a signal is supplied to the input terminal, the instruction information receiving unit 64 will not receive the signal. However, in the stylus 2 of this embodiment, the control unit 60 is configured to activate the control signal En based on the reception of the trigger signal US_trg, which is received before the instruction signal US_cmd, thus enabling the reception of the instruction signal US_cmd without problems. This will be explained in detail below.

[0084] The control unit 60 is composed of a microprocessor (MCU). This microprocessor (MCU) performs operations according to a predetermined program by controlling the on / off state of switches SW1 to SW3 based on the control signal SWC, controlling the start state of the instruction information receiving unit 64 based on the control signal En, generating the oscillation control signal Ocn, and performing pen pressure detection based on the pen pressure detection sensor 23. These will be described in detail below.

[0085] It should be noted that the pen pressure detection sensor 23 is a capacitor whose capacitance changes with pen pressure in this embodiment. Regarding pen pressure detection using this capacitor, the method disclosed in Patent Document 3 can be used, so the description is omitted here.

[0086] First, regarding the on / off control of switches SW1~SW3 and the control signal En, the control unit 60 performs the control shown in Table 1 below.

[0087] [Table 1]

[0088] As shown in Table 1, in the initial state (when the stylus 2 is not on the tablet computer 3), the control unit 60 turns on switches SW1 and SW2, turns off switch SW3, and puts the command information receiving unit 64 into a stop state. As a result, electrode 21 is connected to the trigger signal detection unit 63, and thus the receiving operation of the trigger signal US_trg is performed as shown in Table 1. Furthermore, since the command information receiving unit 64 is in a stop state, the power consumption of the stylus 2 can be suppressed.

[0089] Upon receiving the trigger signal US_trg, i.e., after the detection signal Det becomes high, the control unit 60 switches switch SW1 to open and switch switch SW3 to close. Furthermore, the command information receiving unit 64 is activated by activating the control signal En. Regarding switch SW2, it can remain closed or be switched off. Thus, electrode 21 is connected to the command information receiving unit 64, and the command information receiving unit 64 is activated, therefore, the command signal US_cmd is received as shown in Table 1. The control unit 60 temporarily holds the command information Cmd output from the command information receiving unit 64, which receives the command signal US_cmd in this manner.

[0090] Here, the control unit 60 can operate in either a low-speed operation mode (first operation mode) that consumes little power (and a high-speed operation mode) or a high-speed operation mode (second operation mode) that consumes more power (second operation mode). In the low-speed operation mode, the control unit 60 can only receive a simple binary signal, i.e., the detection signal Det, but cannot receive or process complex information such as command information Cmd, or transmit position signals DS_pos and data signals DS_res. When performing these operations, the control unit 60 needs to be in high-speed operation mode. Therefore, in this example, the control unit 60 is preferably configured to automatically switch from the low-speed operation mode to the high-speed operation mode when the detection signal Det changes from a low level to a high level (i.e., when the trigger signal US_trg is received). Furthermore, it is preferable to return to the low-speed operation mode after the data signal DS_res has been transmitted. This minimizes the power consumption of the control unit 60. Hereinafter, the control unit 60 will be described with a structure corresponding to these two modes.

[0091] The control unit 60, which receives the command signal US_cmd and stores the command information Cmd from the command information receiving unit 64, turns on switch SW1 and turns off switches SW2 and SW3. Furthermore, it returns the command information receiving unit 64 to the stop state by setting the control signal En to inactive. The control unit 60 then activates the oscillation circuit 61 (position indication signal transmitting unit) by setting the oscillation control signal Ocn to a high level for a certain period. As a result, a position signal DS_pos (position indication signal) generated continuously for a certain period is sent from electrode 21. During this period, the indicated position of the stylus 2 is determined in the tablet computer 3 by receiving the position signal DS_pos.

[0092] After sending the position signal DS_pos, the control unit 60, while maintaining the states of switches SW1~SW3 and control signal En, outputs an oscillation control signal Ocn to enable the oscillation circuit 61 to generate and store the data signal DS_res corresponding to the instruction information Cmd, and supplies it to the oscillation circuit 61. It should be noted that, through... Figure 3 The data signal DS_res generated by the structure shown becomes an OOK (On-Off Keying) modulated signal. Through the above operations performed by the control unit 60, the OOK modulated data signal DS_res is sent from electrode 21 and received by the tablet computer 3 as described above. Then, the control unit 60 returns to the initial state.

[0093] Regarding how the instruction information receiving unit 64 extracts the instruction information Cmd from the instruction signal US_cmd, refer to... Figure 13 and Figure 14 The output (D0~D11) and clock (CLK) from the AD converter 64a are sent to the matched filter circuit 64b. Figure 14 Input. This clock is the same as the sampling frequency of the AD converter 64a, and is preferably set to... Figure 13 The frequency is an integer multiple of the period of the first step of the spread spectrum symbol shown. In this embodiment, the sampling frequency of the AD converter 64a is shown to be... Figure 13 The case shown is twice the step period of the spread spectrum symbol. Furthermore, a reset signal (not shown) is supplied from the control unit 60, thereby clearing the values ​​(Q0-Q15) of the shift registers (R0-R31) and the registers of the arithmetic unit. In this embodiment, the case where data (D0-D11) from the AD converter 64a is received at the rising edge of the clock (CLK) and the arithmetic unit performs its operations will be described.

[0094] KEY codes (k0~K15) and the command signal US_cmd sent by the tablet computer. Figure 13The spread spectrum code of the ) is also stored as "0x1AD3". That is, in this embodiment, since the transmission starts from the higher-order bits, it becomes k0=1, k1=1, k2=0, k3=0, k4=1. k15=0. In the arithmetic section, the sum of addition or subtraction operations performed on the data stored in shift registers (R0~R31) is calculated and output as Q0~Q15. This output (Q0~Q15) appears as signed data. Here, since k0=1, the values ​​of shift registers R0 and R1 are added to Q0~Q15. Furthermore, since k1=1, the values ​​of shift registers R2 and R3 are added to Q0~Q15. And, since k2=0, the values ​​of shift registers R4 and R5 are subtracted from Q0~Q15. Thus, the results of addition or subtraction operations on the 32 AD conversion results (R0~R31) are output as Q0~Q15. Here, processing is performed on two consecutive values ​​of the shift register (R0~R31) corresponding to the values ​​of k0~K15 because the sampling frequency of the AD converter 64a in this embodiment is... Figure 13 This is because the step period of the spread spectrum symbol shown is twice that of the step period.

[0095] Figure 15 It means Figure 14 A graph showing the relationship between each step (the number of rises of CLK) and the output. After receiving the trigger signal US_trg, the control unit 60 activates the control signal En as shown in Table 1, and then supplies a reset signal (Reset) to the matched filter circuit 64b. As a result, the shift registers (R0~R31) are cleared, and therefore the outputs (Q0~Q15) from the arithmetic unit also become 0. In this embodiment, it is necessary to activate the instruction information receiving unit 64 of the stylus 2 before sending the instruction signal US_cmd from the tablet computer, but here, as Figure 15 The initial clock (CLK) rises after the reset signal (Reset) is added as the instruction signal US_cmd from the tablet. Figure 13 The explanation will begin after the initial sending of the message.

[0096] like Figure 15 As shown, the output (Q0~Q15) of the matched filter circuit 64b exhibits a large positive value at the 32nd step. Furthermore, it exhibits a large negative value at the 64th step. Additionally, it exhibits a large positive value at the 96th step. Therefore, the control unit 60 can detect when the instruction information Cmd sent from the tablet computer is (1, 0, 1).

[0097] The above explains the structure and operation of the stylus 2. Next, refer to... Figure 4 and Figure 5 The processing flow shown is as follows: Figure 6 The timing of transmitting and receiving each signal shown provides an overall explanation of the operation of the position detection device in this embodiment. Figure 4 This is a flowchart illustrating the processing flow of the tablet computer 3 in this embodiment. Figure 5 This is a flowchart illustrating the processing flow of the stylus 2 in this embodiment. Figure 6 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in this embodiment.

[0098] like Figure 4 and Figure 6 As shown, the tablet computer 3 operates by periodically and repeatedly sending trigger signal US_trg and command signal US_cmd. Figure 4 Steps S301 and S303). It should be noted that, in practice, the finger 4 detection action is performed in a time-division manner with the transmission of the aforementioned signal, but the explanation of the finger 4 detection action is omitted here. Hereinafter, Figure 6 At time t1 (the time between the transmission time of the Nth trigger signal US_trgN and the transmission time of the (N+1)th trigger signal US_trgN+1), the stylus 2 is placed (DOWN) on the sensor surface 3a of the tablet computer 3 (refer to...). Figure 1 And continue to explain.

[0099] Stylus 2 repeatedly performs the receiving action of trigger signal US_trg in the initial state. Figure 5 (Steps S401, S403). If the stylus 2 approaches or contacts the sensor surface 3a of the tablet computer 3 at time t1, the trigger signal US_trgN+1 subsequently sent from the tablet computer 3 is received by the stylus 2. Upon receiving the trigger signal US_trgN+1, the state of the control unit 60 first changes from the STOP state (the aforementioned low-speed operation mode) to the RUN state (the aforementioned high-speed operation mode). Figure 5 Step S405. Figure 6 The change occurs at time t2). Figure 3 The detection signal Det shown is achieved by making it high.

[0100] The control unit 60, which is in the RUN state, activates the command information receiving unit 64 by activating the control signal En (into the Enable state). Figure 5 Step S407. Figure 6At time t2). The instruction information receiving unit 64, activated in this way, receives the instruction signal US_cmd sent from the tablet computer 3 following the trigger signal US_trgN+1 (step S409). The control unit 60 then deactivates the control signal En, thereby ending the instruction information receiving unit 64 (becoming Disabled). Figure 5 Step S411. Figure 6 (Time t3).

[0101] Next, the control unit 60 performs processing corresponding to the content of the instruction information Cmd extracted from the instruction information receiving unit 64 that received the instruction signal US_cmd. Figure 5 Step S413). To give a specific example of this process, for instance, if the instruction information Cmd is the information described above for calculating the pen pressure value, the control unit 60 performs the process of transferring the pen pressure value through... Figure 1 The latest pen pressure value P (pen pressure information) obtained by the pen pressure detection sensor 23 shown is set as the data signal DS_res. Moreover, for example, if the instruction information Cmd is information for obtaining the stylus number SID (ID information) inherent to the stylus 2, the control unit 60 performs processing to set the stylus number SID stored in the storage unit (not shown) as the data signal DS_res.

[0102] In addition to the processing performed by the control unit 60 based on the content of the instruction information Cmd, various other processing methods may also be included. For example, it may be configured to detect the position of a slider or similar component provided on the side of the stylus 2 and set it as the instruction information Cmd; it may be configured to change the transmission time of the position signal DS_pos; or it may be configured to change the frequency of the position signal DS_pos or the data signal DS_res.

[0103] Next, the control unit 60 sequentially sends the position signal DS_pos and the data signal DS_res. Figure 5 Steps S415 and S417. Figure 6 The position signal DS_pos1 and data signal DS_res1). The control unit 60, which has stopped transmitting the data signal DS_res, switches from the RUN state (the high-speed operation mode mentioned above) to the STOP state (the low-speed operation mode mentioned above). Figure 5 Step S419. Figure 6 At time t4). On the other hand, after sending the command signal US_cmd, tablet 3 first performs the action of receiving the position signal DS_pos ( Figure 4 Step S305). Furthermore, upon receiving the position signal DS_pos ( Figure 4 After the affirmative determination in step S307, the next step is to receive the data signal DS_res. Figure 4Step S309). When the position signal DS_pos is not received ( Figure 4 Step S307 negation determination), returns the sending of trigger signal US_trg ( Figure 4 Step S301).

[0104] The above completes the series of processes corresponding to the (N+1)th trigger signal US_trgN+1. Then, as... Figure 6 As shown, the same process described above is repeated when the tablet computer 3 sends the (N+2)th trigger signal US_trgN+2. It should be noted that the transmission interval of the trigger signal US_trg from the tablet computer 3 can be constant or variable. Furthermore, the tablet computer 3 can adjust the transmission interval of the trigger signal US_trg based on whether it receives the position signal DS_pos or the data signal DS_res.

[0105] It should be noted that when receiving the position signal DS_pos based on tablet 3, at the initial placement of stylus 2 (DS_pos1), Figure 2 The X and Y electrodes selected by the selection circuit 41 and selection circuit 42 are switched sequentially and the receiving action is performed. The X and Y coordinates of the indicated position of the stylus 2 are calculated by the number of the electrode that obtains the maximum signal level and the distribution of the signal level before and after it.

[0106] In addition, once the indicated position of the stylus 2 is roughly determined (after DS_pos2), it is sufficient to receive the multiple X and Y electrodes in the vicinity that have been determined in advance when the position signal DS_pos is received. The X and Y coordinates of the indicated position of the stylus 2 can be calculated from the distribution of the signal level at that time.

[0107] As described above, according to this embodiment, the stylus 2 does not receive the trigger signal US_trg when it is not on the tablet computer 2, therefore the stylus 2 does not need to send a signal. Thus, compared to conventional active styluses, the battery consumption of the stylus 2 can be suppressed.

[0108] Furthermore, the stylus 2 can be configured to send only the information requested according to the instruction signal US_cmd, thus suppressing the transmission time of signals from the stylus 2.

[0109] Furthermore, according to this embodiment, as the structure of the stylus 2, an instruction information receiving unit 64 is provided for receiving the instruction signal US_cmd, and the content of the data signal DS_res can be changed according to the content of the received instruction information Cmd. Therefore, the inherent ID number, which only needs to be received once, does not need to be sent from the stylus every time, which can shorten the transmission time from the stylus and reduce the power consumption of the stylus.

[0110] In this embodiment, a trigger signal detection unit 63 for detecting the trigger signal US_trg is provided separately from the command signal US_cmd. The command information receiving unit 64 is activated only when the trigger signal US_trg is detected by the trigger signal detection unit 63. Therefore, the operation time of the power-consuming command information receiving unit 64 can be shortened in a very limited way, and the power consumption of the stylus can be further reduced.

[0111] Furthermore, according to this embodiment, the stylus 2 operates in a low-speed mode after the data signal DS_res is transmitted and before the trigger signal US_trg is received, thus reducing the power consumption of the control unit 60. Therefore, compared to conventional active styluses, the power consumption of the stylus 2 can be further reduced.

[0112] Furthermore, according to the stylus 2 of this embodiment, the transformer 62, which uses the coil of the LC resonant circuit 61a for signal transmission as the secondary coil, functions as a bandpass filter. Therefore, compared to the case where a separate bandpass filter is provided for receiving the trigger signal US_trg, the number of components mounted on the stylus 2 can be reduced.

[0113] It should be noted that in this embodiment, spread spectrum symbols are used as the command signal US_cmd sent by the tablet computer, but it is not limited to this. For example, a modulation method that changes the frequency or phase of the transmitted signal according to the transmitted command information Cmd can also be used. In this case, the structure of the command information receiving unit 64 of the stylus 2 also needs to be changed according to the modulation method. Even if other modulation methods are used, the signal detection accompanying decryption usually consumes a lot of power, so the effect of this embodiment is effective.

[0114] Next, the second embodiment of the present invention will be described. The structure of the tablet computer 3 and the stylus 2 in this embodiment is similar to... Figures 1-3 The situation is the same as shown. This embodiment differs from the first embodiment in the order in which the position signal DS_pos and the command signal US_cmd are transmitted. Otherwise, it is the same as the first embodiment; therefore, the following description will focus on the parts that differ from the first embodiment.

[0115] Figure 7 This is a flowchart illustrating the processing flow of the tablet computer 3 in this embodiment. Figure 8 This is a flowchart illustrating the processing flow of the stylus 2 in this embodiment. Figure 9 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in this embodiment.

[0116] like Figure 7 As shown, the control circuit 43 of the tablet computer 3 in this embodiment (refer to...) Figure 2 ) Sending the instruction signal US_cmd ( Figure 7 Before step S303), the position signal DS_pos is received from the stylus 2. Figure 7 In steps S305 and S307), the position of the stylus 2 is detected. The command signal US_cmd is sent only when the position signal DS_pos is received.

[0117] In the stylus 2 of this embodiment, the control unit 60 performs the control shown in Table 2 regarding the switches SW1~SW3 and the control signal En.

[0118] [Table 2]

[0119] Comparing Table 2 with Table 1, it can be seen that in this embodiment, the aspect of transmitting the position signal DS_pos before receiving the command signal US_cmd differs from that in the first embodiment. This also indicates that... Figure 8 In the processing flow of this embodiment, the stylus 2 activates the instruction information receiving unit 64 in the step ( Figure 8 Before step S407), the position signal DS_pos is sent. Figure 8 Step S415).

[0120] To achieve this operation, in this embodiment, after receiving the trigger signal US_trg (i.e., after the detection signal Det becomes high), the control unit 60 switches switch SW2 to open. Switches SW1 and SW3 remain on and off respectively, and the command information receiving unit 64 remains in a stopped state. Furthermore, the position signal DS_pos is transmitted in the same manner as in the first embodiment.

[0121] Immediately after the transmission of the position signal DS_pos ends, the control unit 60 initiates control for receiving the command signal US_cmd. Specifically, the control unit 60 switches switch SW1 to open, switches switch SW3 to close, and activates the control signal En, thereby putting the command information receiving unit 64 into operation. Switch SW2 can remain open or be switched to open. Thus, the command signal US_cmd transmitted by the tablet computer 3 is received by the command information receiving unit 64, and the control unit 60 stores the command information Cmd.

[0122] It should be noted that, although in Figure 7The details are omitted, but the transition from S307 to S303 includes the following processing: When the tablet computer 3 detects the end of the position signal DS_pos, it waits for a certain period of time before starting to send the command signal US_cmd. In the stylus 2, the command information receiving unit 64 is switched to the operating state during the aforementioned time (a certain period of time).

[0123] The control unit 60, which stores the instruction information Cmd, turns on switch SW1, turns off switches SW2 and SW3, and returns the instruction information receiving unit 64 to the operation stop state. Furthermore, it transmits the data signal DS_res corresponding to the instruction information Cmd in the same manner as in the first embodiment.

[0124] like Figure 9 As shown, in this embodiment, the tablet computer 3 first periodically and repeatedly sends the trigger signal US_trg. Furthermore, after the stylus 2, which is placed (DOWN) on the sensor surface 3a of the tablet computer 3 at time t1, receives the trigger signal US_trgN+1 sent from the tablet computer 3, it first causes the control unit 60 to change to RUN state (the high-speed operation mode described above). Figure 9 At time t2), the next step is to generate the position signal DS_pos( Figure 9 The position signal DS_pos1 is transmitted. Furthermore, when the transmission of the position signal DS_pos1 ends, the command information receiving unit 64 is activated (enters the Enable state). Figure 9 At time t3, the instruction signal US_cmd1 sent from the tablet computer 3 is received. Furthermore, after receiving the signal, at time t4, the instruction information receiving unit 64 is deactivated (becomes in a disabled state), and... Figure 6 Similarly, the data signal DS_res1 is transmitted. The control unit 60, having finished transmitting the data signal DS_res, switches from the RUN state (the high-speed operation mode described above) to the STOP state (the low-speed operation mode described above). Figure 9 (Time t5).

[0125] The above describes the series of processes corresponding to the receipt of the (N+1)th trigger signal US_trgN+1 in this embodiment. Then, as... Figure 9 As shown, the tablet computer 3 sends the (N+2)th trigger signal US_trgN+2, repeating the same process described above. It should be noted that in this embodiment, the transmission interval of the trigger signal US_trg from the tablet computer 3 can be constant or variable. Furthermore, the tablet computer 3 can adjust the transmission interval of the trigger signal US_trg based on whether it receives a position signal DS_pos or a data signal DS_res.

[0126] As explained above, in this embodiment, the stylus 2 does not receive the trigger signal US_trg when it is not on the tablet computer 2, therefore the stylus 2 does not need to send a signal. Thus, compared to conventional active styluses, the battery consumption of the stylus 2 can be suppressed.

[0127] In addition, the stylus 2 can be configured to send only the information requested according to the instruction signal US_cmd, thus suppressing the transmission time of the signal from the stylus 2.

[0128] In addition, in this embodiment, the stylus 2 is also structured with an instruction information receiving unit 64 for receiving instruction signal US_cmd. The content of the data signal DS_res can be changed according to the content of the received instruction information Cmd. Therefore, since the inherent ID number does not need to be sent from the stylus every time, the transmission time from the stylus can be shortened and the power consumption of the stylus can be reduced.

[0129] In this embodiment, a trigger signal detection unit 63 for detecting the trigger signal US_trg is set up separately from the command signal US_cmd. The trigger signal detection unit 63 detects the trigger signal US_trg, and the command information receiving unit 64 is started after the position signal DS_pos is sent. Therefore, the operation time of the power-consuming command information receiving unit 64 can be shortened to a very limited extent, and the power consumption of the stylus can be further reduced.

[0130] Furthermore, in the stylus 2 of this embodiment, the control unit 60 is in low-speed operation mode after the data signal DS_res is sent and before the trigger signal US_trg is received, thus reducing the power consumption of the control unit 60. Therefore, compared with conventional active styluses, the power consumption of the stylus 2 can be further reduced.

[0131] In addition, the tablet computer 3 of this embodiment does not need to send the instruction signal US_cmd when the stylus 2 is not on the tablet computer, so it can make good use of the time for other processing, such as the detection processing of the finger 4.

[0132] It should be noted that, in this embodiment, the spread spectrum symbol is also used as the instruction signal US_cmd sent by the tablet computer, but it is not limited to this. Even if other modulation methods are used, the effect of this embodiment is also effective, just as described in the first embodiment.

[0133] Next, the third embodiment of the present invention will be described. The stylus 2 of this embodiment differs from the stylus 2 of the first embodiment in that it constructs the data signal DS_res from the signal after BPSK modulation. Furthermore, along with this difference, the structure of the stylus 2 also differs. It is the same as the second embodiment in other aspects; therefore, the following description will focus on the parts that differ from the second embodiment.

[0134] Figure 10 This is a diagram showing the internal structure of the stylus 2 according to the third embodiment of the present invention. Figure 11 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in the third embodiment of the present invention.

[0135] exist Figure 10 In China, through cooperation with Figure 3 The electrode 21, instruction information receiving unit 64, AD converter 64a, matched filter circuit 64b, amplifier circuit 63a, detector circuit 63b, and pen pressure detection sensor 23, represented by the same symbols, are the same as those in the first embodiment ( Figure 3 (The same structure)

[0136] SW4 is a switch that selects one of three terminals (a, b, and c) and connects to electrode 21. Terminal a is connected to the trigger signal detection unit 71, terminal b is connected to the instruction information receiving unit 64, and terminal c is connected to the boost circuit 74 (described later). The state of switch SW4 is controlled according to the control signal SWC supplied from the control unit 70.

[0137] The transmitting signal generation circuit 73 is a circuit that generates the source signal for the position signal DS_pos and the data signal DS_res based on the modulation signal Mod from the control unit 70. The boost circuit 74 is a circuit that generates the position signal DS_pos and the data signal DS_res by boosting the signal generated by the transmitting signal generation circuit 73 to a certain amplitude.

[0138] The position signal DS_pos in this embodiment is the same as that in the second embodiment, but the modulation method used for the data signal DS_res differs from that in the second embodiment. Various adjustments can be used as the modulation method for the data signal DS_res in this embodiment, but BPSK (Binary Phase Shift Keying) modulation is preferred. Hereinafter, the case where BPSK modulation is used as the modulation method for the data signal DS_res will be described. In this case, the transmission signal generation circuit 73 modulates the modulation signal Mod using BPSK modulation, thereby generating the data signal DS_res.

[0139] The trigger signal detection unit 71 is a structure in which a bandpass filter 71a (filter circuit) centered on a predetermined single frequency is added to the front end of the trigger signal detection unit 63 (the front end of the amplifier circuit 63a). That is, the stylus 2 of this embodiment does not include an LC resonant circuit 61a for signal transmission (see reference). Figure 3 Therefore, in this embodiment, the band limit based on transformer 62, as in the first embodiment, cannot be implemented. Therefore, the bandpass filter 71a removes frequency components outside the frequency band of the trigger signal US_trg from the signal directed to electrode 21. The processing of amplifier circuit 63a and detector circuit 63b is the same as described in the first embodiment.

[0140] In this embodiment, the control unit 70 controls the state of switch SW4 and the operation state of command information receiving unit 64 as shown in Table 3.

[0141] [Table 3]

[0142] As shown in Table 3, in the initial state, the control unit 70 sets switch SW4 to select terminal a and sets the command information receiving unit 64 to a stop state. Furthermore, the mode of the control unit 70 in the initial state is the same as the low-speed operation mode described above in the first embodiment. Therefore, electrode 21 is connected to the trigger signal detection unit 71, and the receiving operation of the trigger signal US_trg is performed as shown in Table 3. Moreover, since the command information receiving unit 64 is in a stop state, the power consumption of the stylus 2 can be suppressed.

[0143] After receiving the trigger signal US_trg, i.e., after the detection signal Det output from the trigger signal detection unit 71 becomes high, the control unit 70 selects terminal c of the switch SW4 and switches its mode to the high-speed operation mode described above. Furthermore, it generates a modulation signal Mod for the transmission signal generation circuit 73 and the boost circuit 74 to generate a single-frequency signal, namely the position signal DS_pos, and supplies it to the transmission signal generation circuit 73. Thus, the position signal DS_pos is output from electrode 21 and received by the tablet computer 3, similar to the second embodiment.

[0144] After sending the position signal DS_pos, the control unit 70 selects terminal b of the switch SW4 and activates the command information receiving unit 64 by turning on the control signal En. As a result, the control unit 70 receives the command signal US_cmd from the command information receiving unit 64, extracts the command information Cmd from the received command signal US_cmd, and saves it.

[0145] Upon receiving the command signal US_cmd, the control unit 70 selects terminal c using switch SW4 and deactivates the control signal En, returning the command information receiving unit 64 to the stop state. Furthermore, a modulation signal Mod is generated to enable the transmission signal generation circuit 73 to generate a data signal DS_res corresponding to the stored command information Cmd, and supplied to the transmission signal generation circuit 73. Thus, the BPSK-modulated data signal DS_res is output from electrode 21 and received by the tablet computer 3, similar to the second embodiment.

[0146] It should be noted that the structure of the tablet computer 3 used in this embodiment is as long as it is Figure 2 The BPSK demodulation circuit can be used instead of the detector circuit 49 and the AD converter 50.

[0147] In this embodiment, as an action of the stylus 2, it is preferable to transmit the data signal DS_res at a timing synchronized with the receiving action of the instruction information receiving unit 64. Specifically, this is because the output of the matched filter circuit 64b is as follows: Figure 15 When outputting in that way, the output value Q0~Q15 exceeds the specified level in the positive or negative direction at a certain timing ( Figure 15 The steps 32, 64, and 96) and the steps from tablet 3 Figure 13 The timing of the transmission of the instruction signal US_cmd is consistent with the timing of the end of the transmission of 1 bit. Therefore, if the data signal DS_res from the stylus is transmitted at the same time, the BPSK signal can be reliably demodulated in the tablet computer 2.

[0148] In this embodiment, the data signal DS_res can be constructed from the signal modulated by BPSK. In other respects, it is the same as the second embodiment; therefore, according to this embodiment, the effect of suppressing battery consumption of the stylus 2 can also be obtained in the same way as the second embodiment.

[0149] It should be noted that in this embodiment, the transmission order of the position signal DS_pos and the command signal US_cmd is the same as in the second embodiment. However, this embodiment can also be configured to transmit the above signals in the same transmission order as the first embodiment.

[0150] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such embodiments in any way. The present invention can, of course, be implemented in various forms without departing from its spirit.

[0151] For example, in the embodiments described above, the stylus 2 is configured to send a data signal DS_res after sending a position signal DS_pos, making the position signal DS_pos essential. However, the first embodiment of the present invention is also well applicable even when the stylus 2 does not send a position signal DS_pos. In this case, the tablet computer obtains the stylus's position information through the data signal DS_res. Figure 12 This situation is illustrated.

[0152] Figure 12 This diagram illustrates the timing of signal transmission and reception between the stylus 2 and the tablet computer 3 in a variation of the first embodiment. As shown in the diagram, in this variation, the stylus 2 transmits the signal DS_others instead of the position signal DS_pos and the data signal DS_res. In the first embodiment, the tablet computer 3 transmits the command signal US_cmd without waiting for the position signal DS_pos to be received, thus making this variation possible.

[0153] Figure 17 This diagram shows the internal structure of the stylus 2, which is a variation of the third embodiment. Figure 18 This is a diagram illustrating the internal structure. In the third embodiment described above, the stylus 2 uses a common electrode 21 for both signal transmission (DS_pos and DS_res) and signal reception (US_trg and US_cmd). However, in the modified example shown here, the electrode 21 provided at the front end of the pen tip 20 is used only for signal transmission (DS_pos and DS_res), and the electrode used for signal reception (US_trg and US_cmd) is separate from the one used for transmission. Figure 17 The electrode 26 shown is a ring-shaped electrode fixed near the front end of the frame of the stylus 2 for receiving purposes.

[0154] Figure 18 The operation of this modified example shown is compatible with that of the third embodiment ( Figure 10 The same applies to Table 3. That is, whenever the control unit 70 performs control to select terminal a in Table 3 (SW4), Figure 18 When SW5 selects terminal a, the control unit 70 controls the selection of terminal b by SW4 in Table 3. Figure 18 Simply select terminal b for SW5. Furthermore, if terminal c is selected for SW4 in Table 3... Figure 18 If terminal b is pre-selected by SW5 and the control signal En is not activated, then electrode 26 is connected to the command information receiving unit 64, and the command information receiving unit 64 does not operate, thereby enabling the same operation as in the third embodiment. Furthermore, SW5 can also be configured to not select either terminal a or terminal b.

[0155] exist Figure 18 In the modified example shown, the electrode 21 used for transmitting is connected to the direct boost circuit 74, thus reducing the capacity of the output terminal of the boost circuit 74 and having the effect of reducing the power consumed by the boost circuit 74.

[0156] In the above embodiments, a battery is used as the power source for the stylus 2, but other methods may also be used, such as a structure that includes a supercapacitor and a charging circuit.

[0157] In addition, in the above embodiments, the pen pressure is transmitted as digital information using OOK modulation or BPSK modulation, but other methods can also be used, such as changing the frequency of the position signal DS_pos according to the pen pressure.

[0158] Symbol Explanation

[0159] 1. Position detection device

[0160] 2. Stylus

[0161] 3 Tablet PCs

[0162] 3a Tablet 3's sensor surface

[0163] 4 fingers

[0164] 20 pen refills

[0165] 20a The front end of the pen refill 20

[0166] Electrodes 21 and 26

[0167] 23 Pen pressure detection sensor

[0168] 24 Circuit board

[0169] 25 batteries

[0170] 30 sensors

[0171] 30X, 30Y linear electrodes

[0172] 31 Sensor Controller

[0173] 41 X Selection Circuit

[0174] 42 Y-select circuit

[0175] 43 Control Circuit

[0176] 43a Trigger signal transmitting unit

[0177] 43b Command Signal Transmitter

[0178] Switches 44 and 45

[0179] 46, 63a Amplifier Circuit

[0180] 47 Gain Control Circuit

[0181] 48, 71a bandpass filters

[0182] Detector circuits 49 and 63b

[0183] 50, 64a AD converters

[0184] 51 MCU

[0185] 60, 70 Control Department

[0186] 61 Oscillating Circuit

[0187] 61a LC resonant circuit

[0188] 62 Transformer

[0189] Trigger signal detection unit 63, 71

[0190] 64. Command Information Receiving Unit

[0191] 64b matched filter circuit

[0192] 73 Signal Generation Circuit

[0193] 74 Boost Circuit

[0194] SW1~SW5 switches

Claims

1. A position detection device, which determines the indicated position of the position indicator on the tablet computer by electrostatic coupling between the tablet computer and the position indicator, characterized in that, The tablet computer is equipped with a first control signal transmitting unit and a second control signal transmitting unit. The first control signal transmitting unit and the second control signal transmitting unit are used to transmit two control signals with different frequencies or modulation forms to the position indicator. The location indicator includes: a power supply unit; a location indication signal transmitting unit for transmitting at least a location indication signal to the tablet computer; and a first control signal receiving unit for receiving a first control signal transmitted from the first control signal transmitting unit. and a second control signal receiving unit, configured to receive a second control signal transmitted from the second control signal sending unit. The first control signal causes the position indicator to perform a first control action, and the second control signal causes the position indicator to perform a second control action, which is different from the first control action. The first control signal is a specified single-frequency, unmodulated signal. The second control signal is a signal modulated using specified binary data. The first control signal is a trigger signal. The second control signal is a command signal. When the position indicator moves more than a predetermined distance away from the tablet computer, neither the position indication signal nor the second control signal is transmitted; only the first control signal is received. The position indicator has inherent ID information and a pen pressure detection circuit, and transmits a data signal modulated according to the pen pressure information detected by the pen pressure detection circuit or the inherent ID information. The position indicator selects the inherent ID information, the pen pressure information, or other information based on the content of the received second control signal, and sends the data signal modulated according to the selected information.

2. The position detection device according to claim 1, characterized in that, The first control signal receiving unit is equipped with a filter circuit centered on the specified single frequency.

3. The position detection device according to claim 1 or 2, characterized in that, The second control signal is obtained by spreading the specified binary data using spread spectrum symbols.

4. The position detection device according to claim 1 or 2, characterized in that, The second control signal is a signal obtained by frequency modulation of the carrier wave using the specified binary data.

5. The position detection device according to claim 1 or 2, characterized in that, The position indicator includes a first operating mode that only receives the first control signal and a second operating mode that at least repeatedly transmits the position indicator signal and receives the second control signal. In the first operation mode, upon receiving the first control signal, the system transitions to the second operation mode.

6. The position detection device according to claim 1 or 2, characterized in that, The tablet computer is configured to send the second control signal in response to the transmission of the first control signal.

7. The position detection device according to claim 1 or 2, characterized in that, The position indicator sends the position indication signal after receiving the first control signal. The tablet computer is configured to send the second control signal after the location indication signal ends.

8. The position detection device according to claim 1, characterized in that, The data signal sent by the position indicator is a signal that has been OOK modulated.

9. The position detection device according to claim 1, characterized in that, The data signal sent by the position indicator is a BPSK modulated signal.

10. A position indicator that determines the indicated position on a tablet computer via electrostatic coupling with the tablet computer, characterized in that, Given: Power supply unit; The location indication signal transmitting unit transmits at least a location indication signal to the tablet computer; The first control signal receiving unit receives a first control signal of a specified frequency sent from the tablet computer. and The second control signal receiving unit is used to receive a second control signal modulated with specified binary data sent from the tablet computer. The first control signal causes the position indicator to perform a first control action, and the second control signal causes the position indicator to perform a second control action, which is different from the first control action. The first control signal is a specified single-frequency, unmodulated signal. The first control signal is a trigger signal. The second control signal is a command signal. When the position indicator moves more than a predetermined distance away from the tablet computer, neither the position indication signal nor the second control signal is transmitted; only the first control signal is received. The position indicator has inherent ID information and a pen pressure detection circuit, and transmits a data signal modulated according to the pen pressure information detected by the pen pressure detection circuit or the inherent ID information. The position indicator selects the inherent ID information, the pen pressure information, or other information based on the content of the received second control signal, and sends the data signal modulated according to the selected information.

11. The position indicator according to claim 10, characterized in that, The first control signal receiving unit is equipped with a filter circuit centered on the specified frequency.

12. The position indicator according to claim 10 or 11, characterized in that, The second control signal receiving unit is configured to receive a signal generated by spreading the specified binary data using spread spectrum symbols.

13. The position indicator according to claim 10 or 11, characterized in that, The second control signal receiving unit is configured to receive a signal generated by frequency modulation of a carrier wave using the specified binary data.

14. The position indicator according to claim 10 or 11, characterized in that, The position indicator includes a first operating mode that only receives the first control signal and a second operating mode that at least repeatedly transmits the position indicator signal and receives the second control signal. In the first operation mode, upon receiving the first control signal, the system transitions to the second operation mode.

15. The position indicator according to claim 1, characterized in that, The data signal is a signal that has been modulated by OOK.

16. The position indicator according to claim 1, characterized in that, The data signal is a signal that has been modulated by BPSK.

17. A position indicator that determines the indicated position on a tablet computer via electrostatic coupling with the tablet computer, characterized in that, Given: Power supply unit; transformer; The signal generation circuit generates a signal at the resonant frequency of the resonant circuit composed of the primary winding and capacitor of the transformer. The electrode is connected to the secondary side of the transformer; as well as The control signal receiving circuit receives control signals sent from the tablet computer and directed to the electrode via an input terminal connected to the secondary side of the transformer.

Images